To finish a single leg with a double leg, let go of the leg you're struggling with when the opponent's sprawl stalls you out, and attack the other one with both hands. Two hands on one leg is twice as powerful as one hand on each — and the double leg finish is right there.
Jon Trenge breaks this down in the video above, and the logic is airtight.
The single leg is the most-scored-with move in wrestling. The double leg is the second-most-scored offensive move. The reason the single scores more often isn't that it's a better shot — it's that when a double gets stuffed, most wrestlers try to hold both legs and end up face-planting. "If the guy has a good sprawl to your double, don't try to hold both legs, or your face is going to be the only thing posting you off the mat."
Release one leg. Go to a single.
And the reverse works too. When you're on a head-outside single and he's shutting you down, you can swing through to a double and run it. Jon calls it "a double off of a single" — same technique, reversed direction.
Here's Jon's favorite setup to get you into a double in the first place. He calls it raking the head.
Your back hand grabs the CROWN of his head — not the top, or you slip off. Dig your fingertips in right where the head rounds the corner and grab it like a cantaloupe. Don't just yank. Actually break his head down, pushing it between his own legs. That's the mistake experienced wrestlers make — they pull instead of rake.
He's going to swat at your hand. Good. That's the reaction you want. Your opposite hand comes up, he snaps his head back to escape, and NOW his legs are loaded and you pick your shot. Cut-across double. Spear double. Low double. Whichever one his stance gives you.
Flick his head to the side first. It gives you an angle and pulls him off center so he's defending an imaginary opponent. Then drive across.
Head outside. Heel, toe, knee. Sweep the legs out, finish ninety degrees to the side.
For the full breakdown, check out our guide on the arm drag to single leg takedown. The complete course is in Jon Trenge's Complete Wrestling System.